"Not that surely," said MacNair, "but scientists knowing that magnetic currents often pass more readily through opaque than transparent substances, began to search for rays of this kind that would pass through dark bodies and be reflected by substances beyond. At last they succeeded in securing a photograph through wood and metal, and then, all that was required in order to enable us to see through opaque matter, was an optical instrument that would cast the reflection on the retina of the eye. This, in the course of time, was accomplished. And now, these wonderful discoveries are used by the medical profession, in order to enable them to look into the bodies of their patients and examine the internal organs. And, these electro-magnetic optical instruments have been so improved that they are in general use, in observations where opaque bodies obstruct the view." "And do you tell me this as sober truth?" I asked. "Certainly," responded MacNair, "I propose to give you a practical demonstration. You discovered that the space between us and the zenith was opaque to your vision. Now, take these glasses and adjust them to your eyes and look through those semi-transparent sections, which are like a lace-work of tubes. The penetrating power of these glasses, you see, can be increased or decreased by moving this slide. They enable you to use the magnetic rays which pass through all substances for the purpose of vision." We followed his directions and the first glance gave us an ocular demonstration that the surface was concave. "Now," continued MacNair, "in order to get the best idea of the leading geographical outlines of this inner world, I want you to examine with your glasses a zone from the horizon in front of us, through the zenith to the horizon behind us. We are now moving on an airline for your future home in Altruria. Our course is a little south of west and the distance about one thousand miles. We are now very near the center of the Oscan ocean. East of us is the continent of Atlan. So, a zone, extending through the zenith along the line on which we are moving will pass through the equatorial belt, and give you a clear concept of the great centers of population and material improvement. This is the most important part of the world for you to study for the present, and until you learn the language and mingle with the people, you must depend upon your eyes as the chief source of information."